AU658996B2

AU658996B2 - Fire detector

Info

Publication number: AU658996B2
Application number: AU37123/93A
Authority: AU
Inventors: Yasuo Ariga; Eiji Hirooka
Original assignee: Nohmi Bosai Ltd
Current assignee: Nohmi Bosai Ltd
Priority date: 1992-04-25
Filing date: 1993-04-22
Publication date: 1995-05-04
Anticipated expiration: 2013-04-22
Also published as: EP0569712B1; US5486816A; AU3712393A; DE69317147D1; EP0569712A1; CN1049993C; CA2094736A1; DE69317147T2; CA2094736C; CN1077810A

Description

AUSTRALIA

Patents Act 1 990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT P/00/01 1 Regulation 3.2 *9 *9 S 9 9* 9* 9 9 9 9 9 Invention Title: FIRE DETECTOR The following statement is a full description of this invention, including the best method of performing it known to us: S 69 *9 GH&CO REF: P22700-D:DAA:RK 1 433 FIRE DETECTOR BACKGROUND OF THE INVENTION FIELD OF THE INVENTION: The present invention relates to a fire detector and, more particularly, to a photoelectric type iire detector capable of photoelectrically detecting smoke generated as a result of a fire, as well as to a heat-photoelectric type fire detector which detects occurrence of fire by sensing both heat and smoke generated by the fire.

DESCRIPTION OF THE RELATED ART A photoelectric type smoke detector is known from, for example, the disclosure of Japanese Patent Publication No. 63- 34520. This device has a housing composed of a detector body and a cover fitting on the body. A printed circuit board is provided on the bottom of the body. An optic base is disposed in an opening formed in the upper side of the housing. The optic base carries a light-emitting element and a lighte receiving element arranged such that the optical axes of these elements are nearly in parallel with the optic base. A top plate with a labyrinth is placed through the opening in the upper side of the housing so as to cover the optic base. The outer peripheral surface of the top plate with labyrinth is covered with a bug screen.

Assembling and disassembling of this known smoke detector requires a laborious work, and are time-consuming due to the use of so many screws as fixing means. The optic base in the opening of the housing is held by a support member bent in an L-shaped so as to be spaced from the printed circuit board in order to protect electric circuit parts. Consequently, the height of the housing is increased by the height of the L-shaped support member. The thickness of the detector could be reduced by reducing the height of a dark box which is formed on the optic base. This solution, however, may lead to impairment of the performance of the detector. Therefore, the dark box is inevitably designed to have an ordinary height, and the overall thickness of the smoke detector is increased accordingly.

Fixing of the L-shaped support member to the printed circuit board also requires a troublesome work. In addition, the support member tends to be deformed, which makes it difficult to fix the optic base at a preselected distance from the printed circuit board. Displacement of the optic base may cause a misalignment of optical axis between the light emitting element and the light receiving element.

In general, a photoelectric type smoke detector employs a shield case made of, for example, an iron sheet which electrostatically and electromagnetically shields the light receiving element in order to prevent erroneous operation attributable to noise induced by electromagnetic waves or the like. The use of such a shield case, however, increases noise light components because the light emitted from the lightemitting element, as well as the light reflected by the inner surface of the dark box, impinged upon and reflected by the shield case, thus impairing precision of detection. In order to II 'I overcome these problems, the shield case is usually painted in black color.

The use of a shield case painted in black poses the following problems.

A: The shield case is to be soldered to the printed circuit board directly at its legs or indirectly through lead wires. Therefore, the portions where the soldering is done should be left unpainted or, alternatively, the paint on these portions should be removed before soldering. Either of them are troublesome.

B: Assembling of the detector requires the greatest care so as not to damage the shield case by, for example, an assembly tool, otherwise the noise light components increase due to scattering of light by the damaged portion of the shield case where the paint is removed.

C: Dust accumulated in the dark box is to be removed in periodical inspection of the smoke detector. This essentially eooo requires detaching and attaching of a lid of the dark box. The cleaning work must be done with the greatest care so as not to 0 damage the paint on the shield case by the lid or a cleaning tool.

.In general, a known smoke detector employs, as the light-emitting element, a so-called bullet type diode having a substantially hemispherical top portion and a pair of lead terminals extending downward from the lower end. This type of diode emits light such as infrared light rays upward or forward from the hemispherical top portion. This type of light-emitting -3t I diode is laid in the smoke detector in such a manner as to emit the light substantially in parallel with the bottom wall of the dark box or at a certain angle thereto. This essentially requires that the lead terminals of the diode are bent at a certain angle. Consequently, the assembling of this known smoke detector requires a work for bending the lead terminals of the light emitting diode at a certain angle. In addition, excessive force might possibly be applied to the main part of the diode, when bending the terminals, and cause the diode to be destroyed.

Practically, it is difficult to bend the lead terminals of all light-emitting diodes precisely at the same angle. In other words, the bending angle varies with each individual diode. Such variation in bending angle causes offset of the mounting height of the diode when the lead terminals are soldered to the printed circuit board. This leads to misalignment of the optical axis of the light-emitting diode with that of the light-receiving element, impairing the precision of smoke detection.

Attempts have been made to obviate the variation in the mounting height of the light emitting diode, such as to insert and fix the light-emitting diode in a diode holding portion provided in the dark box, or to fix the diode on the diode holding portion by means of a retainer plate. Such fixing methods, however, are not recommended because the light-emitting diode could be destroyed or the life of the same shortened due to force applied to the lead terminals during the fixing.

In general, it is not possible to bend the lead -4terminals at their base ends. Consequently, the overall length of the light-emitting diode in the state of use is increased, ch undesirably impedes reduction in the diameter of the dark box, making it difficult to design and produce a compact smoke detector.

A heat-photoelectric type fire detector is also known in which the above-described smoke detecting function is combined with fire detecting function sensitive to heat. This combined type fire detector employs a heat sensing element projected to the outside of the housing through an opening in the cover. The lead wires of the heat sensing element are fixed to the top plate having the labyrinth by means of an adhesive tape.

In this type of fire detector, it has been difficult to precisely locate and fix the heat sensing element at a predetermined position, due to the use of the adhesive tape for fixing the lead wires. In addition, the heat sensing element, even when placed at the predetermined position, tends to be

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shifted if the lead wires are pulled, thus impairing precision of the fire detection.

SUMMARY OF THE INVENTION An aim of the present invention is to ameliorate at least some of S. the problems of the prior art.

It is an advantage that the present invention provides a photoelectric type fire detector or a heat-photoelectric type fire detector, which is thin and facilitates assembly and disassembly.

It is a further advantage that the present invention embodies a photoelectric type fire detector in which an optic base can be securely and easily fixed to a printed circuit board.

It is yet another advantage that the present invention may provide a photoelectric type fire detector which suppresses mis-alignment of optical axis between the light-emitting element and the light-receiving element.

It is a further advantage that the present invention embodies a photoelectric type fire detector having a shield which can shield the light-receiving element without impairing smoke detecting function.

A still further advantage of the prosent invention is that a photoelectric type fire detector may be provided which does not necessitate bending of the lead terminals of the light-emitting element.

It is a further advantage that the present invention embodies a heat-photoelectric type fire detector which allows easy fixing of the heat sensing element at a desired location.

In a first aspect of the present invention there is provided a photoelectric type fire detector comprising; a printed circuit board having a first side and 25 a second side; a light-emitting element and a light-receiving gos: element which are mounted on the printed circuit board; holding means having a first portion which holds the light-emitting element and a second portion which holds the light-receiving element; and an optic base portion having a first surface and a second surface, the first surface of the optic base portion being arranged immediately adjacent to the second S.side of the printed circuit board, and the optic base portion further having first and second sections which house the first and second portions of the holding means, 0respectively, "e wherein the holding means is arranged between the optic base and the second side of the printed circuit board and a space which is accessible to smoke emanating 700OOD -6from outside the fire detector is formed between the light-emitting element and the light-receiving element so as to be able to receive a beam of light which is substantially parallel to the second side of the printed circuit board and which originates from the lightemitting element, and wherein the light-receiving element is arranged to detect the light when the light is scattered in the space by the smoke when present.

In one embodiment of the present invention, there is provided a photoelectric type fire detector, comprising: a detector body; a printed circuit board disposed on the upper side of the detector body; conductive connecting members provided on the lower side of the detector body; terminal screws for simultaneously fixing the printed circuit board and the conductive connecting members to the detector body; an optic base directly placed on the upper side of the printed circuit board and having a labyrinth formed on the upper side thereof; fixing means for fixing the optic base to the upper side of the printed circuit board; a light-emitting element and a light-receiving element arranged in a pair for detecting smoke; a bug screen provided on the outer periphery of the labyrinth of the optic base; an optic base cover covering the upper side of the optic base; and a 25 protective cover covering the printed circuit board, the optic base, the bug screen and the optic base cover, the protective cover having a plurality of smoke inlet windows and provided with hooks formed on the lower end thereof, the hooks engaging with the detector body 30 thereby fixing the protective cover to the upper side of the detector body.

The present invention also embodies a photoelectric type fire detector, comprising: a printed circuit board having a plurality of insertion holes; an optic base 35 having a plurality of hooks formed on the lower end thereof and having also an annular labyrinth formed on an upper portion thereof, the hooks being received in the insertion holes in the printed circuit board so as to fix the optic base to the upper surface of the printed ,40 circuit board; an optic part holder clamped between the 'I a 4 so 0 0 a.

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a ji r S: OOD-- 1 ,r0 7 optic base and the printed circuit board; and a lightemitting element and a light-receiving element arranged in a pair on the optic part holder.

Advantageously the present invention embodies a photoelectric type fire detector, comprising: a detector body; an optic base directly fixed to the printed circuit board and having an annular labyrinth formed on the periphery thereof; an optic base cover for covering the upper side of said labyrinth of the optic base thereby forming a dark box; and a light-emitting element and a light-receiving element arranged in a pair in the box such that the optical axes of the elements intersect each other.

In another embodiment of the present invention, there is provided a photoelectric type fire detector, comprising: a printed circuit board; a dark box formed on the printed circuit board; a light-emitting element and a light-receiving element arranged in a pair within the dark box; a shield case covering the light-receiving element; and a light interrupting wall formed in the dark box and concealing the shield case.

In a further embodiment of the present invention, there is provided a photoelectric type fire detector, comprising: a dark box having a light-emitting element '.25 receiving portion and a light-receiving element receiving 9 portion formed therein; a side-emission type light- **Got: emitting element received in the light-emitting element receiving portion; and a light-receiving element received in the light-receiving element portion.

S 30 In a second aspect of the present invention there is provided a heat sensitive photoelectric type fire detector comprising a photoelectric type fire detector :according to the first aspect of the present invention with a heat sensing element which is electrically connected to the printed circuit board.

Accordingly the present invention also embodies a .9 rr heat-photoelectric type fire detector, comprising: a detector body; a printed circuit board disposed on S:22700D 8 I I, the upper side of the detector body; conductive connecting members provided on the lower side of the detector body; terminal screws for simultaneously fixing the printed circuit board and the conductive connecting members to the detector bodiy; an optic base directly placed on the upper side of the printed circuit board and having a labyrinth formed on the upper side thereof; fixing means for fixing the optic base to the upper side of the printed circuit board; a light-emitting element and a light-receiving element arranged in a pair for detecting smoke; a bug screen provided on the outer periphery of the labyrinth of the optic base; an optic base cover covering the upper side of the optic base and having a holder receiving portion formed in the upper side thereof; a heat sensing element 0 having lead lines connected to the printed circuit board; a heat sensing element holder holding the heat sensing element and fittingly received in the holder receiving portion of the optic base cover; and a protective cover covering the printed circuit board, the optic base, the bug screen and the optic base cover, the protective cover having a plurality of smoke inlet windows 0* and provided with hooks formed on the lower end thereof, the hooks engaging with the detector body thereby fixing the protective cover to the uppear side of the detector body, the protective cover further having an insertion hole formed in an upper portion thereof such that the heat sensing element protrudes upright through the insertion hole.

Advantageously, the present invention also embodies a heat-photoelectric type fire r-9- /W w detector, comprising: a printed circuiL board; a dark box formed on the printed circuit board; a light-emitting element and a light-receiving element arranged in a pair in the dark box; a holder receiving portion formed in the central portion of the upper side of the dark box and having a plurality of locating recesses; a heat sensing element holder having a plurality of projections received in the locating recesses in the holder receiving portion, the holder being received in the holder receiving portion; a heat sensing element held upright on the holder and having lead lines connected to the printed circuit board; and a protective cover having an insertion hole formed in an upper portion thereof and covering the upper side of the printed circuit board and the dark box, such that the heat es sensing element projects through the insertion hole.

The features and advantages of the present invention will become clea from the following description of the preferred embodiments when the same is read see: in conjunction with the accompanying drawings.

o* C.0 BRIEF DESCRIPTION OF THE DRAWINGS 006 •Figs. 1 and 2 are a plan view and a bottom plan view, respectively, of a photoelectric type fire detector according to a first embodiment of the present invention; Fig. 3 is a sectional view taken along the line A-A of Fig. 1; Fig. 4 is an assembly diagram showing a printed circuit board, an optic part holder, an optic base, an optic P r base cover, a bug screen, a light-emitting element and a lightreceiving element of the first embodiment; Fig. 5 is an assembly diagram of an optic part holder; Figs. 6, 7 and 8 are a sectional view, a plan view and a bottom plan view of the optic base, respectively; Fig. 9 is a sectional view of the optic base cover; Fig. 10 is an assembly diagram showing a detector body, printed circuit board and so forth; Fig. 11 is a perspective view of a protective cover used in the first embodiment; Fig. 12 is a plan view of a heat-photoelectric type fire detector as a second embodiment of the present invention; Fig. 13 is a sectional view taken along the line B-B of Fig. 12; Fig. 14 is a perspective view of the second embodiment illustrating the manner in which the heat sensing element is mounted; o Fig. 15 is a sectional view taken along the line C-C of Fig. 14; and SSI Fig. 16 is a perspective view of a protective cover used in the second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS o* First Embodiment: Referring to Figs. 1 and 2, a photoelectric type fire detector as the first embodiment of the present invention has a detector body 1 and a protective cover 60 which covers the upper -11side of the body 1. As shown in Fig. 3, a plueality of blade matal members 5 serving as conductive joint members are attached to a lower surface lb of the body 1, and a printed circuit board is mounted on an upper surface la of the body 1. The printed circuit board 10 and the blade matal members 5 are fixed to the body 1 by means of common terminal screws 6. An optic part holder 20, an optic base 40 and an optic base cover 50 are secured to the upper surface of the printed circuit board The optic part holder 20 holds an LEr 30 as a light-emitting element, a lens 32, a photodiode 35 as the light-receiving element, and a shield case 37 which shields the photodiode A bug screen 46 is arranged in such a way as to surround the outer periphery of the optic base The photoelectric type fire detector of the first embodiment is assembled in the following manner. As shown in Fig. 4, the LED 30, lens 32, photodiode 35 and the shield case 37 are mounted on the optic part holder 20, and the optic part holder 20 carrying these components is inserted into a hollow formed in the bottom of the optic base 40. The optic base 40 is S then secured to the printed circuit board The optic part holder 20 has a substantially L-like form, and is provided at its one end with a light-emitting element receiving portion 22, a lens receiving portion 23 and a light-emitting window 24 which are arranged in the order of mention from the peripheral part towards the center, as will be seen from Fig. 5. The other end of the holder 20 has, from the peripheral end toward the center, a light-receiving element receiving portion 25, a shield case receiving portion 28 and a lower light shielding wall 29 having a light-receiving window.

Vertical insertion holes 22a and 25a are formed in the bottom of the light-emitting element receiving portion 22 and the lightreceiving element receiving portion 25, in communication with the spaces inside these recaiving portions 22 and 25. The holder 20 has a flat bottom surface 20a. The receiving portions 22 and 25 are opened at their upper sides so as to receive the light-emitting element 30 and the light-receiving element inserted from the upper side.

The LED 30 is of so-called side emitting type element which has an optical axis perpendicular to the element axis, and is provided at its lower portion with vertical lead terminals 31. The use of this type of element eliminates the necessity of bending the lead terminals, thus facilitating the mounting work.

The lens 32 is provided at its upper and lower portions with supporting portions 33 and 34. The photodiode 35 also has an 9*9**9 optical axis perpendicular to the diode axis, and is provided at its lower end with vertical lead terminals 36. The shield case 37, which is not painted, is provided in the front wall thereof with a light-receiving window 38. The upper ends of the lightemitting element 30, lens supporting portion 33 and the shield case 37 constitute contact portions 30a, 33a and 37a at which these elements are pressed onto the optic base The optic base 40 has a construction as shown in Figs.

6 to 8. A light-emitting section receiving portion 41 opened at its lower end, a light-receiving section receiving portion 42 -13which also is opened at its lower end and a light interrupting pillar 43 are provided in and on the bottom surface 40a of the optic base 40. Both receiving portions 41 and 42 are formed in alignment with the corresponding receiving portions in the optic part holder 20. The inner surface of the light-emitting section receiving portion 41 has a contact portion 41a which contacts the light-emitting element 30 and a groove 45 which receives the lens 32 in pressure contact therewith. The inner surface of the light-receiving section receiving portion 42 has an upper light interrupting wall 44 which contacts a lower light interrupting wall 29 of the holder 20, and a contact portion 42a which makes pressure contact with the shield case 37. A labyrinth 47 are annularly arranged on the bottom surface 40a of the optic base so as to sandwich each of the light-emitting section receiving portion 41 and the light-receiving section receiving portion 42. A bug screen 46 is provided over the outer periphery of the labyrinth 47 and held by an annular wall 49.

"The annular wall 49 is provided on the outer side of the optic base 40, and the upper end 49a of the annular wall 49 is located at a lower portion of the labyrinth 47. Three hooks 48, which SeS are spaced in the circumferential direction, are provided on the outer wall of the optic base o The upper surface 10a of the printed circuit board has a cross-shaped shield portion 11 having a large area, check

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terminals 12, an optic base mounting portion 13 formed on the shield portion 11 and an indicator lamp 14. Surface-mountingtype electric circuit parts 10e are provided on the lower -14surface 10b of the printed circuit board 10. Holes 17 for receiving the hooks 48 of the optic base 40 are formed in the printed circuit board 10. A retaining portions 17a for engaging the hooks 48 are formed in the periphery of the insertion holes 17 on the lower surface 10b of the printed circuit board In assembling the fire detector, the side-emitting type light-emitting element 30 is received in the light-emitting element receiving' portion 22, with the lead terminals 31 inserted into the insertion hole 22a formed in the optic part holder 20, and the mount 34 of the lens 32 is placed in the lens receiving portion 23. In this state, the light-emitting element and its lead terminals 31 are held vertically. Then, the light-receiving element 35 is placed in the light-receiving element receiving portion 25, with the lead terminals 36 inserted into the insertion hole 25a. In this state, the lightreceiving element 35 and the lead terminals 36 are held S. vertically. Then, the shield case 37 is fitted in the shield case receiving portion 28 so as to cover and shield the lightreceiving element Subsequently, as shown in Fig. 4, the hooks 48 of the optic base 40 are inserted into the insertion holes 17 in the printed circuit board 10 and are made to engage with retaining portions 17a. Consequently, the optic base 40 is held in direct contact with the printed circuit board 10 at ts bottom surface while being centered by the three hooks 48. Thus, the optic part holder 20 is clamped between the optic base 40 and the printed circuit board 10, while the optic base 40 is correctly located on the optic base mount portion 13.

In this state, the contact portions 30a, 33a and 37a of the light-emitting element 30, a supporting portion 33 of the lens 32 and the shield case 37 on the optic part holder 20 are pressed by the respective contact portions 41a, the groove and contact portions 42a in the optic base 40, so that these elements are correctly located and rigidly held in position even if subjected to any force such as vibration. Thus, the common optical axis L of the light-emitting element 30 and the lightreceiving element 35 is accurately held in parallel with the bottom surface 40a of the optical base 40. The optical axis L is positioned substantially at the same level as the upper end 49a of the annular wall 49.

Subsequently, the bug screen 46 9 placed on the outer peripheral surface of the labyrinth 47 of the optic base 40 so as to be held by the annular wall 49. Then, the optic base 9 cover 50 is attached to the upper side of the optic base eo" The construction of the optic base cover 50 will be described with reference to Fig. 9. Au will be seen from this Figure, a central cylindrical protrusion or wall 51 and a peripheral protrusion or wall 52 are formed on the upper surface of the cover 50, while a plurality of projections 54 are formed on the lower surface of the same. When the cover 50 is attached to the labyrinth 47, the projections 54 of the cover are fitted in associated holes 47b, 41b and 42b formed on the upper surface of the labyrinth 47, light-emitting section receiving portion 41 and light-receiving section receiving -16portion 42, respectively.

As a result, the interior of the space confined by the optic base 40 and the cover 50 is darkened, thus forming socalled dark box. In this state, the shield case 37 is not exposed to the smoke supervising space S because it is surrounded by the light-receiving section receiving portion 42 and the upper light interrupting wall 44 of the optic base and by the lower light interrupting wall 29 of the optic part holder 20. Therefore, the light scattered in the dark box is never reflected by the shiel' case 37, even if the latter is not painted. According to the described arrangement, a sufficiently large distance can be preserved between the upper and lower inner surfaces of the dark box, and the height of the top surface of the dark box from the lower surface of the detector body 1 can be decreased.

Then, as shown in Fig. 10, the printed circuit board 10 and the four blade metal members 5 are secured to the body 1 by means of four terminal screws 6. Four supporting pillars 3 having insertion holes 2, as well as a locating projection 9 for locating the printed circuit board 10, are formed on the upper surface la of the body 1. A retaining portion 4 is provided in the outer periphery of the body 1. As shown in Fig. 2, a water drainage annular groove 1R is formed in the lower surface lb of the body 1, in communication with a drainage hole 1H which is formed in the outer peripheral edge of the body 1. Blade metal members 5 as conductive connecting member shown in Fig. 10 are fixed on the lower surface lb of the body 1. Each blade metal -17member 5 has a fixing portion 5a and a blade portion 5b. The fixing portion 5a is provided with a threaded hole 7 for screwing engagement with the terminal screw 6. The blade portion 5b is adapted to be engaged with a matting blade member which is a conductive connecting member provided on a detector base which is not shown.

The printed circuit board 10 is placed in contact with the top ends of the supporting pillars 3, with the projection 9 received in a hole formed in the printed circuit board Then, the terminal screws 6 are inserted into the holes 2 and 18. Then, the fixing portions 5a of the blade metal members are brought into contact with the lower surface lb of the body 1, and the terminal screws 6 are tightened, whereby the printed circuit board 10 is fixed.

Then, the protective cover 60 as shown in Fig. I or Fig. 1 is fixed to the body 1. The protective cover 60 has a flange portion 61 and a top plate 63 which are connected to each other through connecting stays 62. A check bar insertion hole 64 and an indicator lamp hole 66 are formed in the flange portion 61, and a plurality of smoke inlet windows 65 are provided between the flange portion 61 and the top panel 63.

Hooks are provided on the outer peripheral edge of the flange portion 61 for engagement with retaining portions 4 formed on the body 1.

The protective cover 60 is fixed to the body 1 with the hooks 67 in engagement with the retaining portions 4 of the body 1. The indicator lamp hole 66 receives an indicator lamp -18- 14 which is prcided on the printed circuit board The described construction of the first embodiment is only illustrative. For instance, the lower surface 40a of the optic base 40 may be provided with an annular ring which is adapted to be held in contact with the printed circuit board although the lower surface 40a is in direct contact with the printed circuit board 10 in the described embodiment.

Alternatively, a plurality of circumferentially spaced projections, three projections, may be formed in place of the annular ring. The check termainals 12 may be formed by a print pattern on the printed circuit board 10. The check bar insertion hole 64 formed in the protective cover 60 may be omitted. Matting blade members may be used as the conductive connecting members.

The first embodiment having the described construction offers an advantage over the known devices in that the assembling and disassembling of the detecting device can be done easily because of the reduced number of fixing screws. In addition, since the optic base is directly fixed to the printed circuit board by engaging means, it is possible to reduce the *e thickness of the detector while maintaining a sufficiently height of the dark box. It is thus possible to reduce the *:Do thickness of the detector without giving any adverse effect on

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its performance.

Second Embodiment: Figs. 12 and 13 are a plan view and a sectional view -19of a heat-photoelectric type fire detector which is a second embodiment of the present invention. The second embodiment is similar to the first embodiment hut is different from the latter in that a heat sensing element 70 is provided on the optic base cover 50 and a protective cover 161 is used in place of the protective cover 60 used in the first embodiment. Other components are substantially the same as those in the first embodiment and, therefore, are denoted by the same reference numerals as those in the first embodiment.

Referring to Fig. 14, the upper surface of the optic base cover 50 has a Lolder receiving portion 51 for holding the heat sensing element 70, a lead wire guide groove 55 and a cylindrical portion 52. The holder receiving portion 51 has a cylindrical form, and three lczating recesses 51a are formed in the holder receiving portion 51 at an equal circumferential spacing. The cylindrical portion 52 is provided on the outer e peripheral edge of the optic base cover 50, and has a height 5, S. substantially the same as that of the holder receiving portion 51, The heat sensing element 70 is supported by a heat sensing element holder 71 and is connected at its end to a lead wire 72.

The heat sensing element holder 71 has a insertion hole 71a through which the lead wire 72 or the heat sensing element 70 is inserted. Projections 71b formed on the outer peripheral

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portion of the heat sensing element holder 71 fit in the locating recesses 51a formed in the holder receiving portion 51.

The heat sensing element 70 is secured to the optic base cover 50, after the cover 50 is mounted on the optic base As will be seen from Figs. 14 and 15, the lead wire 72 is inserted into the hole 71a in the heat sensing element holder 71 and, with the heat sensing element 70 held in vertical posture, the lead wire 72 is bent in an L-like form. Then, the heat sensing element holder 71 is moved towards the holder receiving portion 51 of the optic base cover 50 so as to fit the projections 71b into the locating recesses 51a, while fixing the lead wire 72 in the lead wire guide groove 55. In this state, the heat sensing element holder 71 is correctly secured in the center of the optic base cover 50 by means of the projections 71b and the locating recesses 51a. The lead wire 72 are connected to the printed circuit board The construction of the protective cover 160 will be described with reference to Figs. 12 and 16. The protective cover 160 has a flange portion 161 and a top plate 163 connected to the flange portion 161 through connecting stays 162. A hole 9 163a for inserting the heat sensing element 70 is formed in the center of the top plate 163. The lower surface of the top plate 163 constitutes a pressing portion 163b. The flange portion 161 has a check bar insertion hole 164 and an indicator lamp hole 166 formed therein. A plurality of smoke inlet windows 165 are provided between the flange portion 161 and the top plate 163.

o. A plurality of hooks for engagement with retaining portions 4 of s the detector body 1 are provided on the outer peripheral edge of 00 a the flange portion 161. A protective ring 169 for protecting the heat sensing element is provided on the top plate 163 and is connected to the latter through supporting stays 168.

-21- Projections 169a are formed on the lower surface of the protective ring 169 so as to prevent a finger or the like from inserting into the space where the heat sensing element is installed through gaps formed between adjacent supporting stays 168.

In assembling the detector, the protective cover 160 is moved towards the optic base cover 50 and the heat sensing element holder 71 is inserted into the hole 163a formed in the top plate 163 so that the heat sensing element holder 71 and the optic base cover 50 are pressed by the pressing portion 163b of the top plate 163, while bringing the hooks into engagement with the retaining portions 4 of the detector body 1, In this state, the heat sensing element holder 71 is securely fixed so that the heat sensing element 70 can be held at the predetermined position so as to stand upriLght from the center of the top plate 163. In addition, the lead wire 72 is concealed inside the 0* connecting stay 162 of the protective cover 160, without being exposed to the exterior.

The described construction of the second embodiment is only illustrative. For instance, the lower surface 40a of the optic base 40 may be provided with an annular ring which is adapted to be held in contact with the printed circuit board although the lower surface 40a is in direct contact with the printed circuit board 10 in the described second embodiment.

Alternatively, a plurality of circumferentially spaced projections, three projections, may be formed in place of the annular ring. The check terminals 12 may be formed by a -22print pattern on the printed circuit board 10. The check bar insertion hole 64 formed in the protective cover 160 may be omitted. Matting blade members may be used as the conductive connecting members.

The second embodiment having the described construction offers an advantage over the known devices in that the assembling and disassembling of the detector can be done easily because of the reduced number of fixing screws. In addition, since the optic base is directly fixed to the printed circuit board by engaging means, it is possible to reduce the thickness of the detector while maintaining a sufficient height of the dark box. It is thus possible to reduce the thickness of the detector without giving any adverse effect on its performance.

In addition, the heat sensing element is always held at the design position, by means of the holder and the lead wire

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guide groove on the optic base cover, the holder fittingly holding the support member of the heat sensing element, the lead i..

wire guide groove fittingly receiving the lead wire, with the support member pressed by the inner surface of the top plate of the protective cover.

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Claims

1. A photoelectric type fire detector comprising; a printed circuit board having a first side and a second side; a light-emitting element and a light-receiving element which are mounted on the printed circuit board; holding means having a first portion which holds the light-emitting element and a second portion which holds the light-receiving element; and an optic base portion having a first surface and a second surface, the first surface of the optic base portion being arranged immediately adjacent to the second side of the printed circuit board, and the optic base portion further having first and second sections which house the first and second portions of the holding means, respectively, wherein the holding means is arranged between the optic base and the second side of the printed circuit board and a space which is accessible to smoke emanating from outside the fire detector is formed between the light-emitting element and the light-receiving element so as to be able to receive a beam of light which is substantially parallel to the second side of the printed circuit board and which originates from the light- 0 25 emitting element, and wherein the light-receiving element is arranged to detect the lighc when the light is scattered in the space by the smoke when present.

2. A photoelectric type fire detector according to clainL 1 wherein the beam of light has a longitudinal axis 30 which lies in a plane extending substantially perpendicularly with respect to the second side of the oi printed circuit board and wherein the light-receiving element faces the plane. '140:00 soot SO 0024

3. A photoelectric type fire detector according to claim 1 or 2 wherein the first surface of the optic base portion is in direct contact with the second side of the printed circuit board.

4. A photoelectric type fire detector according to any one of claims 1 to 3 wherein the light-emitting element has an optical axis which is substantially perpendicular to a longitudinal axis of the light- emitting element.

5. A photoelectric type fire detector according to claim 4 wherein the longitudinal axis of the light- emitting element extends substantially perpendicularly with respect to the second side of the printed circuit board.

6. A photoelectric type fire detector according to claim 4 or 5 wherein the iight-re.eiving element has a longitudinal axis which extends substantially perpendicularly with respect to the second side of the printed circuit board and an optical axis which is substantially perpendicular to the longitudinal axis of the light-receiving element, and wherein the optical axis of the light-emitting element and the optical axis of the light-receiving element intersect.

90.09. 7. A photoelectric type fire detector according to 25 any one of claims 1 to 6 wherein the light-emitting S• element is a side emitting photodiode. *o. 8. A photoelectric type fire detector according to any one of claims 1 to 7 further comprising a light- interrupting wall portion which is arranged between the S 30 light-receiving element and the space. e 9. A photoelectric type fire detector according to any one of claims 1 to 8 further comprising a shield case 0which covers the light-receiving element. 0. 0099 g~y 25 A photoelectric type fire detector according to any one of claims 1 to 9 wherein the holding means has a third portion for holding a lens and the optic base portion has a third section which receives an upper portion of the lens, and wherein the third portion of the holding means is formed between the first portion and the second portion and the lens is positioned between the light-emitting element and the space. 11. A photoelectric type fire detector according to any one of claims 1 to 10 further comprising a shield case which covers the light-receiving element and wherein the shield case is housed in the second section of the optic base portion. 12. A photoelectric type fire detector according to claim 11 further comprising a light interrupting wall which is arranged between the shield case and the space and which is formed by a first wall portion extending from the optic base portion and a second wall portion extending from the holding means. 13. A photoelectric type fire detector according to any one of claims 1 to 12 further comprising a labyrinth which is formed around at least a part of an outer periphery of the space. :000., S. 14. A photoelectric type fire detector according to .I 25 claim 13 wherein the labyrinth is formed by a plurality of labyrinth members which extend from the second surface of the optic base portion. A photoelectric type fire detector according to ".any one of claims 1 to 12 further comprising a bug screen 30 which surrounds the light-emitting element, the light- receiving element and the space. 26 16. A photoelectric type fire detector according to claim 13 or 14 further comprising a bug screen which surrounds the light-emitting element, the light-receiving element, the labyrinth and the space. 17. A photoelectric type fire detector according to claim 16 wherein the optic base portion has a peripheral wall and the bug screen is arranged between the labyrinth and the peripheral wall. 18. A photoelectric type fire detector according to any one of claims 1 to 17 further comprising fixing means which holds the first surface of the optic base portion against the second side of the printed circuit board. 19. A photoelectric type fire detector according to claim 18 wherein the fixing means comprises a plurality of hooks formed on the optic base portion and the printed circuit board has a plurality of holes which receive the respective said hooks, and wherein the first surface of the base portion is held against the second side of the printed circuit board by the reception of the hooks in the holes. A photoelectric type fire detector according to any one of claims 1 to 19 wherein a light interrupting member is formed in the space between the light-receiving element and the light-emitting element. 25 21. A photoelectric type fire detector according to claim 20 wherein the light interrupting member is a column portion which extends from the second surface of the optic base portion. 22. A photoelectric type fire detector according to 30 any one of claims 1 to 21 further comprising a mounting o portion having a first side and a second side wherein the first side of the printed circuit board is fixed to the tt1 second side of the mounting portion. '~~OOD 27 23. A photoelectric type fire detector according to claim 22 further comprising a plurality of conductive members which are attached to the first side of the mounting portion. 24. A photoelectric type fire detector according to any one of claims 1 to 23 wherein the printed circuit board has a plurality of check terminals which enable the operation of an electrical circuit formed on the printed circuit board to be checked. 25. A photoelectric type fire detector according to claim 24 wherein the operation of the electrical circuit can be checked when a check bar is placed in electrical contact with the check terminals. 26. A photoelectric type fire detector according to any one of claims 1 to 25 further comprising a base portion cover which is connected to the optic base portion and which covers the space formed between the light-emitting element and the light-receiving element. 27. A photoelectric type fire detector according to claim 26 wherein the base portion cover has a plurality of projections which are fitted in respective openings formed in the optic base portion to thereby secure the base portion cover to the optic base portion. S. S 28. A photoelectric type fire detector according to S 25 claim 13, 14, 16 or 17 further comprising a base portion cover which is connected to the optic base portion and covers the labyrinth and the space formed between the light-emitting element and the light-receiving element. e41 SS S:2 0 S22 5 *5 S S~ S.270D2 29. A photoelectric type fire detector according to any one of claims 26 to 28 further comprising a protective cover having one or more smoke inlet openings which allow the smoke to enter the fire detector and wherein the protective cover houses the base portion cover, the optic base portion and the second side of the printed circuit board. A heat sensitive photoelectric type fire detector comprising a photoelectric type fire detector as defined in any one of claims 1 to 25 with a heat sensing element which is electrically connected to the pr.i.nted circuit board. 31. A heat sensitive photoelectric type fire detector according to claim 30 wherein the heat sensing element is electrically connected to the printed circuit board by lead wires. 32. A heat sensitive photoelectric type fire detector according to claim 30 or 31 further comprising a base portion cover which is connected to the optic base portion and which covers the space formed between the light-emitting element and the light-receiving element. 33. A heat sensitive photoelectric type fire detector according to claim 32 wherein the base portion cover has a plurality of projections which are fitted in S25 respective openings formed in the optic base portion to ei e thereby secure the base portion cover to the optic base f ee portion. o• 34. A heat sensitive photoelectric type fire S: detector according to claim 32 or 33 wherein the heat 30 sensing element is held in a holding portion which is :e received in a receiving portion formed on the base cover. 4' SS:22700D 29 A heat sensitive photoelectric type fire detector according to claim 34 wherein the receiving portion is formed on an upper side of the base portion cover. 36. A heat sensitive photoelectric type fire detector according to claim 35 wherein a lead wire guide channel is formed on the upper side of the base portion cover and extends from the receiving portion to an edge of the base portion cover and wherein the lead wires lie in the lead wire guide channel. 37. A heat sensitive photoelectric type fire detector according to any one of claims 32 to 36 further comprising a protective cover having an insertion hole through which the heat sensing element projects and an elevated protective ring portion which is arranged above the heat sensing element. 38. A heat sensitive photoelectric type fire detector according to claim 37 wherein the protective cover has one or more smoke inlet openings which allow the smoke to enter the fire detector and wherein the protective cover houses the base portion cover, the optic base portion and the second side of the printed circuit board. 39. A photoelectric type fire detector substantially 25 as herein described with reference to figures 1 to 11 of the accompanying drawings. goo S. 40. A heat-sensitive type fire detector substantially as herein described with reference to figures 4 to 8 and 10 to 16 of the accompanying drawings. 6 *e Dated this 6th day of February 1995 S.By NOHMI BOSAI LTD. By their Patent Attorney GRIFFITH HACK CO. S:22700D 30 ABSTRACT OF THE DISCLOSURE A photoelectric type fire detector has: a detector body; a printed circuit board disposed on the upper side of the detector body; conductive connecting members provided on the lower side of the detector body; terminal screws for simultaneously fixing the printed circuit board and the conductive connecting members to the detector body; an optic base directly placed on the upper side of the printed circuit board and having a labyrinth formed on the upper side thereof; fixing means for fixing the optic base to the upper side of the printed circuit board; a light-emitting element and a light- receiving element arranged in a pair for detecting smoke; a bug screen provided on the outer periphery of the labyrinth of the optic base; an optic base cover covering the upper side of the f optic base; and a protective cover covering the printed circuit board, the optic base, the bug screen and the optic base cover, the protective cover having a plurality of smoke inlet windows and provided with hooks tormed on the lower end thereof, the *e hooks engaging with the detector body thereby filing the protective cover to the upper side of the detector body. Disclosed also is a heat-photoelectric type fire detector in 9 6 which a heat sensing element connected to the printed circuit board is combined with the photoelectric fire detecting function, the heat sensing element being securely fixed by a protective cover of the device.